GitLab notifications in Rocket.Chat — without Slack

No Slack account. No middleware. Just GitLab → Rocket.Chat. 🚀

A beginner-friendly walkthrough for forwarding GitLab events into a Rocket.Chat channel, using the legacy GitLab “Slack notifications” integration and a Rocket.Chat Incoming Webhook. You don't need to install or subscribe to Slack.

The compatibility path was verified end to end on a self-managed GitLab instance: an actual GitLab Test settings notification arrived in Rocket.Chat. Your GitLab/Rocket.Chat versions and configuration may behave differently.

Warning

Compatibility trick, not a forever API. GitLab deprecated Slack notifications in 15.9 and hides it for some previously unconfigured projects in 19.5. For new or long-lived deployments, see the native GitLab Webhooks alternative. This repository documents a working path, not a promise of long-term support.

Architecture

flowchart LR
    A[GitLab project] --> B[Slack notifications integration]
    B -- HTTPS POST / Slack-shaped payload --> C[Rocket.Chat Incoming Webhook]
    C --> D[Channel notifications]
    E[Slack service] -. not involved .- B

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5-minute quickstart

1 — Create a bot user in Rocket.Chat

Open Manage → Workspace → Users and create or choose a dedicated account such as gitlab-bot.

• Ensure it exists, is active, and belongs to the target channel, e.g. #dev-notifications.
• In Manage → Workspace → Permissions, verify that its role has message-impersonate. Rocket.Chat requires this when the integration uses impersonation features.
• Prefer a minimally privileged bot to an administrator account.

2 — Create a Rocket.Chat Incoming Webhook

Go to Manage → Workspace → Integrations → New → Incoming, and set:

Setting	Example
Enabled	On
Name	GitLab Notifications
Post to Channel	#dev-notifications
Post as	gitlab-bot (real existing username)
Alias	GitLab (optional display label)
Script Enabled	Off for this compatibility method
Allow override destination channel	Off unless explicitly needed

Save. Copy the generated webhook URL into your password manager. Treat the entire URL as a credential. Never commit it, paste it in an issue, or include it in screenshots.

3 — Test Rocket.Chat independently of GitLab

Run from your machine:

bash scripts/test-webhook.sh

The script prompts for your webhook URL without echoing it, sends examples/payload.json, prints the HTTP response status, and does not write the URL to disk. Expect an HTTP 2xx response and a message in the channel. This validates only the Rocket.Chat side.

4 — Allow outbound access on GitLab Self-Managed (if needed)

If GitLab says:

Webhook is blocked: Requests to the local network are not allowed

its SSRF defense has likely stopped the request because the webhook hostname resolves to a private IP.

As a GitLab administrator open Admin → Settings → Network → Outbound requests. In Local IP addresses and domain names that hooks and integrations can access, allow only the necessary endpoint, ideally restricted to HTTPS:

chat.example.internal:443

Keep Allow requests to the local network from webhooks and integrations disabled globally, and keep Enforce DNS-rebinding attack protection enabled. Don't allow 192.168.0.0/16 or the entire LAN. If the address is resolved inside Docker, verify the destination DNS and routing from the GitLab container, too. See Troubleshooting.

5 — Configure GitLab Slack notifications

Navigate to Project → Settings → Integrations → Slack notifications:

Setting	Value
Active	On
Webhook	Your Rocket.Chat Incoming Webhook URL
Username	GitLab (optional)
Triggers	Merge request, Issue, Pipeline, Deployment, etc.
Channel overrides	Leave blank to use the Rocket.Chat integration's destination
Notify only broken pipelines	Consider enabling to reduce noise
Notify only when status changes	Consider enabling

Save changes, then click Test settings (or use the available test action on your GitLab version). Confirm that the message reaches Rocket.Chat. Only that final test validates the full path.

Tip

Project → Group → Instance: GitLab supports configuring Slack notifications at these levels. For many projects, consider a group-level integration instead of duplicating configuration everywhere. Check inherited settings before enabling both, or you may get duplicates.

Success checklist

• A normal HTTPS curl POST arrives in the Rocket.Chat room.
• Post as refers to a real user with channel membership and message-impersonate permission.
• GitLab outbound policy allows only the needed destination (if it resolves privately).
• The GitLab integration saves without a blocked-webhook error.
• GitLab Test settings creates a real Rocket.Chat message.
• A real merge request / pipeline event sends the expected notification.
• The webhook URL is stored securely and has never appeared in version control.

Troubleshooting

Symptom	Likely cause	Fix
Invalid user [error-invalid-user]	Invalid Post as user	Create the user or set a valid username
The user must exist and have the message-impersonate permission	Missing bot permission / membership	Verify role permissions and channel membership
Webhook is blocked: Requests to the local network are not allowed	GitLab SSRF guard blocks private destination	Allowlist the specific hostname and port as admin
curl works, GitLab fails	Different DNS, routing, or outbound policy	Test from GitLab container and check outbound settings
HTTP 200 but no visible message	Wrong channel, integration, or formatting	Check Rocket.Chat channel and integration logs
Slack notifications is missing	Deprecated/hidden integration	Use native GitLab Webhooks

Full diagnosis: docs/troubleshooting.md.

Native alternative for new deployments

GitLab project/group Webhooks → Rocket.Chat Incoming Integration with a GitLab event transformation script. It avoids relying on the deprecated Slack notifications interface and is documented by Rocket.Chat. See docs/native-webhooks.md. It needs an integration script; simply pointing GitLab's raw JSON at a scriptless Rocket.Chat incoming webhook is not equivalent.

Local validation

bash -n scripts/*.sh
python3 -m unittest discover -s tests -v

No dependencies for repo tests. Only bash and curl are required to send the live webhook test.

Documentation / sources

• GitLab — Slack notifications (deprecated)
• GitLab — Filtering outbound requests
• Rocket.Chat — Incoming Integrations
• Rocket.Chat — GitLab native Webhooks

Security and credits

This is an independent community guide, not an official GitLab, Rocket.Chat, or Slack project. No tokens, internal server addresses or private infrastructure details are bundled. Found a security issue? See SECURITY.md.

Made by CodeCorn Technology — documenting the errors we hit so you don't have to. 🌽

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